Acinetobacter equi sp. nov., isolated from horse faeces

Area of Science:

• Microbiology
• Bacteriology
• Genomics

Background:

• The genus Acinetobacter comprises several species, including those found in animal feces.
• Accurate taxonomic classification is crucial for understanding microbial diversity and function.

Purpose of the Study:

• To taxonomically characterize five bacterial strains isolated from horse feces.
• To determine if these strains represent a novel species within the Acinetobacter genus.

Main Methods:

• 16S rRNA gene sequencing for initial phylogenetic analysis.
• Whole-genome sequencing and core gene phylogeny reconstruction.
• Analysis of DNA G+C content, polyamine profiles, fatty acid composition, and ubiquinone.
• Phenotypic characterization including Gram staining, morphology, aerobic respiration, and substrate utilization tests.

Main Results:

• The five strains shared identical 16S rRNA gene sequences and exhibited phenotypic characteristics consistent with the Acinetobacter genus.
• Whole-genome analysis placed the isolates closest to Acinetobacter bouvetii, but distinct enough to warrant new species status.
• Unique genomic DNA G+C content (34.9 amol%) and a low proportion of C18:1ω9c fatty acids differentiated the strains.
• Distinctive metabolic capabilities, including l-arabinose and gentisate utilization, and inability to grow above 41°C, further supported their novelty.

Conclusions:

• The five horse fecal isolates represent a novel species, named Acinetobacter equi sp. nov.
• Acinetobacter equi is distinguishable from other validly published Acinetobacter species by a combination of genomic and phenotypic traits.
• This finding contributes to the understanding of bacterial diversity in equine environments.